Describe how a swab is taken and sent for culture of Group B Streptococcus (GBS) to provide the highest rate of detection of colonisation. (3)
Vaginal swab - self swab (don’t use speculum) 2cm into vagina
Don’t touch cotton bud end
Then insert swab into anus- 1cm
Swab at 35-37/40
• Place in sterile medium tube of selective enrichment broth, label, send with form requesting GBS culture with pt name, NHI, details and gestation.
• Should be processed as soon as possible.
Describe and evaluate two different strategies for the prevention of early onset neonatal GBS disease. (8 marks)
. Universal Screening
- All women are screening with LVS/anogenital swab for GBS at 35-37 weeks gestation.
- If GBS positive on swab:
o IAP (intrapartum antibiotic prophylaxis) is given
o Recommend immediate IOL if SROM at term
- If GBS negative on swab:
o No IAP required
- Exceptions:
o No IAP required for elective C/S with intact membranes even if GBS positive (but swab should still be done in case of SROM prior to elective date)
o Women with previous affected baby with GBS sepsis or GBS bacturia in current pregnancy should not be swabbed as should receive IAP regardless as result
Benefits:
- Studies have shown decreased rates of early onset GBS sepsis in neonates, RR 0.46 (although decrease in mortality not shown)
- Will pick up more women colonised with GBS
- Likely cost effective
Disadvantages:
- More expensive
- More labour intensive
- Medicalisation of pregnancy and labour
- Need for greater resources to facilitate immediate IOL for SROM at term
- Some women will be given antibiotics unecessarily
- Antibiotic allergies can occur
- Some women will be missed e.g. late bookers/unbooked women
. Risk Based Screenng
- No routine swabs for GBS
- Women should be given IAP if:
o Previous GBS infected neonate
o Previous GBS bacturia (any colony count) in this pregnancy
o GBS on swabs done for another reason in the pregnancy (unless has had LV at 35-37 weeks which is negative)
o Ruptured membranes >18hrs
o Maternal fever >38 degrees or clinical chorioamnionitis
o Preterm labour <37 weeks gestation
Advantages:
- Cheaper
- Fewer unnecessary antibiotics given
- Fewer cases of anaphylaxis/allergic reaction
- Can apply to any woman who presents in labour
- Although less effective, still low EOGBS rate
Disadvantages:
- May miss some GBS postive women
- Less effective at protecting against EOGBS
Discuss the antibiotics used for intrapartum chemoprophylaxis of early onset neonatal GBS disease. (4 marks)
IV antibiotics should be given in labour if GBS positive or risk factors for EOGBS infection.
Aim for at least 4 hours prior to delivery, so give when in active labour until delivery.
Suggested regime from ASID: (however other local guidelines may differ)
- 1st line – benzylpenicillin 3g IV loading dose then 1.8g IV q4 hourly (penicillin preferred over amoxicillin as narrower spectrum of cover)
- Penicillin hypersensitivity without history of anaphylaxis:
o Cefazolin 2g IV loading dose then 1g q8hrly
- Penicillin or cephalosporin allergy at risk of anaphylaxis:
o Clindamycin 600mg IV q8hrly (ask for sensitivities at time of sending swab if penicillin allergic as 20% clindamycin resistance of GBS), OR
o Vancomycin 1g IV q12hrly
o (Erythromycin no longer an acceptable alternative - resistance rates of 30%).
- If signs of maternal sepsis broaden antibiotic cover to:
o Amoxycillin 2g IV q6hrly, PLUS
o Gentamicin 4-6mg/kg IV daily, PLUS
o Metronidazole 500mg IV q12hrly
If delivered by elective pre rupture of membranes C/S – not required.
- Regarding GBS:
a) maternal carriage is 50%
b) neonatal sepsis is rare if the mother is clinically well
c) 10% of babies born of carrier mothers are sick
d) if isolated from amniotic fluid with PPROM should give antibiotics and deliver
e) treat and wait
D
Colonisation of the genital tract with GBS occurs in ~ 20% of women
Early onset GBS occurs at a rate of 1-2% per 1000 live births (although declining)
The later in pregnancy that culture are performed, the better the correlation with culture results at delivery (particularly within 5 weeks of delivery)
Detection of GBS is increased by up to 25% by collecting an anorectal swab in addition to a vaginal swab.
90% of neonates with early onset GBS have onset of signs within 12 hrs of birth (suggesting intrauterine transmission) so intrapartum antibiotic prophylaxis is the most effective means of prevention.
Rate of maternal anaphylaxis to penicillin is estimated at 1 in 100,000
Alternatives to penicillin
o clindamycin 600mg IV 8h
o erythromycin 500mg IV 6h
Duration of intrapartum prophylaxis is inversely proportional to the percentage of babies colonised with GBS
- What organism causes chancroid?
a) Calymmatobacterium granulomatis
b) Haemophilus Ducreyi
c) Gardnerella vaginalis
d) Chlamydia trachomatis
e) Calymmatobacterium donovae
B
Chancroid
o Haemophilus Ducreyi
o Base may have grey or yellow exudate
o Painful
o Detection – gram stain or PCR
o Treatment – Azithromycin 1gm stat or ceftriaxone 250mg IM
o 50% inguinal adenopathy – often painful
- What organism causes Donovanosis?
a) Calymmatobacterium granulomatosis
b) Haemophilus Ducreyi
c) Gardnerella vaginalis
d) Chlamydia trachomatis
e) Calymmatobacterium donovae
Answer a
Donovanosis / Granuloma Inguinale
o Calymmatobacterium granulomatosis
o Usually painless
o Diagnosed on Wright stain for Donovan bodies
o Treatment – azithromycin 1gm orally once a week for 4/52
- What causes LGV (lymphogranuloma venereum)?
a) Calymmatobacterium granulomatis
b) Haemophilus Ducreyi
c) Gardnerella vaginalis
d) Chlamydia trachomatis
e) Calymmatobacterium donovae
Answer d LGV o Chlamydia trachomatis L1-L3 o Adenopathy – matted clusters o Treatment – doxycycline 100bd for 21 days or azithromycin 1g stat
- Your 16w patient has a Mantoux reaction of 16mm. She is asymptomatic and CXR is normal. What is the best management?
a) Vaccinate with BCG
b) Reassure and review postnatally
c) Isoniazid 300mg daily for 6 months
d) Isoniazid 300mg daily for 12 months
e) Rifampicin 100 mg daily for 12 months
Answer b
A positive test is presumptive evidence of current or prior infection or prior BCG vaccination.
If recent close contact with an active case or with known or suspected HIV infection – 5mm or more of induration is considered positive, other problems >10mm, all others (low risk) >15mm.
Patients with a positive test should be evaluated with a CXR
For management see Prologs question 42
If no recent exposure then isoniazid 300 mg daily for 6 months post-natally
- PID with temp. 39 degrees and bilateral pelvic tenderness. Chlamydia on swabs. Best therapy:
* **
a) IM Cephalothin and PO doxy
b) PO doxy alone
c) IV cefoxitin and PO doxy
d) IV clindamycin
e) IV penicillin + erythromycin
c) IV cefoxitin and PO doxy
- All of the following statements about HSV II are true except:
* **
a) infection with HSV I confers some immunity from HSV II
b) treatment with acyclovir significantly reduces recrudescence
c) genital herpes is mostly HSV II
d) recrudescence occurs in the first 6 months
B
- In an acute tubo-ovarian mass, most common culture is:
* **
a) group b strep
b) gonococcus
c) Chlamydia
d) Anaerobes
e) E.coli
D
What are the risk factors for acquiring primary HSVII in pregnancy?
- Unprotected sexual intercourse with infected partner, especially if active lesions at the time
- Young adults have highest risk of new infection
What is the risk of vertical transmission of HSVII in a woman who acquires primary infection in late gestation?
~50%
What is the risk of vertical transmission of HSVII in a woman who has an active recurrence of HSVII at the time of labour?
1-3%
What is the risk of vertical transmission of HSVII in a woman who has a recurrence of HSBVII with no lesions at the time of labour?
<0.01%
How would you reduce vertical transmission of HSVII?
• If first episode within 6 weeks of delivery:
o Recommend elective C/S
o If SROM prior recommend urgent C/S, but may not confer additional benefit if SROM >4 hrs
o Paediatric assessment of neonate and prophylactic acyclovir
• If recurrent infection, consider suppressive acyclovir from 36/40 gestation
o If lesions present at time of delivery (do speculum exam):
Counsel about mode of delivery – can have vaginal birth if wishes, as low risk (1-3% of vertical transmission)
Avoid FSE/FBS/ARM/instrumental
o If no lesions at time of delivery:
Reassure vaginal birth safest
Avoid FSE/FBS/ARM/instrumental
Explain the characteristics of Listeria monocytogenes that account for this rare infection being 20 times more common in pregnant women than in the general population. (2 marks)
- Cell-mediated infection is a primary host defence against listeria – a gram positive bacillus.
- Reduced cell-mediated immunity in pregnancy leads to higher susceptibility.
- Listeria has a low virulence in general population.
Justify the food safety advice given to pregnant women to prevent listeria infection. (4 marks)
• Avoidance of foods that could contain listeria:
- Unpasteurised milk/soft cheeses – pasterurisation kills listeria
- Uncooked meat/fish – cooking kills listeria
- Pre-prepared salads – may have become cross-contaminated with listeria and have time to replicate
• Safe food handling
- Cook food thoroughly – kills listeria
- Rinse fruits/veges well – remove listeria from surface (the bacteria is found in soil)
- Store ‘high risk’ foods away from ‘safe’ foods – avoid cross-contamination
A 30 year old primigravid presents at 28 weeks having consumed a product that has recently been recalled because of contamination with listeria. She is extremely anxious for her health and that of her baby.
b. Formulate a detailed response for this patient to address these concerns:
Clinical features (3 marks) Perinatal effects (3 marks) Management (3 marks)
Clinical features - enquire and educate about these:
• Fever, flu-like illness, general malaise, abdominal/loin pain, back ache, diarrhoea, sore throat, conjunctivitis.
• If severe – ARDS, meningitis, encephalitis, septicaemia. May be asymptomatic (approx. 1/3).
Perinatal effects:
• Transmission is highest in 3rd trimester and has 40-50% mortality for fetus.
• Miscarriage/IUFD, perinatal mortality, PPROM, PTL, chorioamnionitis, meconium stained liquor. Neonatal – pneumonia, meningitis. However, may also have no affect.
Management:
- Admit to hospital for observation and supportive management.
- Maternal diagnosis – blood cultures and gram stain and cultures of genital tract (serology unhelpful)
- Antibiotics – PO amoxycillin/ampicillin if mild. IV amoxycillin/ampicillin and gentamicin if severe (not sensitive to cephalosporins). Duration of 14 days.
- Consider delivery after steroids if severe (weigh risks of infection vs risks of permaturity).
- Notifiable disease to Public Health services.
List specific groups of women at an increased risk of acquiring Parvovirus B19 infection in pregnancy (1 mark)
- Women with children affected at home (50% risk if susceptible, compared to exposure in general community of 20%)
- Women working in daycares or schools who are in contact with children who may be affected (20-30% risk if susceptible)
In women who have Parvovirus B19 infection during pregnancy:
i) Explain the pathogenesis of fetal disease (2 marks)
- Affects erythroid precursors, where it is cytotoxic, which can result in severe anaemia, which in turn can cause cardiac failure and contribute to hydrops
- Infects hepatic cells causing hypoalbuminaemia and myocardial cells causing cardiomyopathy, which contributes to hydrops
- May infect megakaryocytes which can cause thrombocytopenia
In women who have Parvovirus B19 infection during pregnancy:
ii) Outline the potential fetal clinical sequelae including likelihood of occurrence (4 marks)
- Fetal anaemia 10-25%, can resolve spontaneously
- Non-immune hydrops 3-12%
- IUFD may occur without hydrops 5-10% (highest risk 2nd trimester)
- Rarely myocarditits, fetal arrhythmia, brain injury
A 27 year old G2P1 who is now 17 weeks pregnant has been referred to you by her GP because she has recently been exposed to a confirmed diagnosis of “slapped cheek syndrome” (Parvovirus B19 infection). She has no symptoms and has not yet had any tests performed.
c. Outline and justify your approach to this women.
i) To diagnose or refute maternal parvovirus infection (4 marks)
• Maternal serology:
o IgG +ve, IgM –ve = immune, reassure, no action required
o IgG -ve, Ig M–ve = susceptible
Repeat IgG 2-4 weeks after exposure/symptoms
• –ve, reassure not recent infection, no action required however remains susceptible
• +ve confirms recent infection
o IgG –ve, IgM +ve = ? recent infection
Repeat IgG 2-4 weeks after exposure/symptoms
• -ve then the IgM was false positive, reassure not recent infection, no action required, however remains susceptible
• +ve confirms recent infection
o IgG +ve, IgM +ve = recent infection
• +/- newer diagnostic techniques such as IgG avidity and epitope-type specificity assays may be more sensitive and specific however not widely available
A 27 year old G2P1 who is now 17 weeks pregnant has been referred to you by her GP because she has recently been exposed to a confirmed diagnosis of “slapped cheek syndrome” (Parvovirus B19 infection). She has no symptoms and has not yet had any tests performed.
c. Outline and justify your approach to this women.
ii) To manage proven parvovirus infection in pregnancy (4 marks)
Maternal:
• Monitor FBC due to risk of anaemia if immunocompromised or has hereditary blood disease
• Monitor for risk of Mirror Syndrome secondary to hydrops if this develops (preeclampsia like syndrome)
• Otherwise reassurance, no intervention for mother required
Fetus:
• No intervention is available to prevent fetal infection or damage
• Termination is not indicated because of low risk of fetal damage
• Ultrasound should be performed at 1-2 weekly intervals for 12 weeks to detect fetal anaemia or hydrops including Doppler assessment MCA PSV
o If fetal anaemia detected refer to specialist experience in fetal ultrasound, blood sampling and IUT. 84% of fetuses with severe hydrops will survive if treated with IUT. Long term sequelae is rare.
o If no fetal abnormality after 30 weeks then no further action required
Overall candidates showed poor knowledge of Parvovirus B19, one of the five common childhood exanthemas. Maternal infection in the first 20 weeks can cause fetal anaemia with the potential cause of fetal harm through miscarriage or hydrops in up to 15% of these pregnancies. There is no vaccination available, so serological immune status of both Parvovirus B19 IgG and IgM is used to assess the risk to or infective status of a pregnant woman. Management of an acute infection includes weekly ultrasound assessment to diagnose fetal anaemia by raised MCA PSV or the presence of hydrops. If anaemia is detected, referral to a fetal medicine unit is indicated for fetal blood transfusion. There is no preventative therapy. Long term sequelae are rare.
